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Surface Finishing Tutorial

#181 Paint Types - 9

Category : Painting
April 4, 2014

(15) Powder coatings

Powder coatings are synthetic resin compositions in fine powder form with pigments, fillers, curing agents, and plasticizers added to thermosetting or thermoplastic resins.

For the thermoplastic coating resins, there are Vinyl chloride, Polyolefin (polyethylene), Polyamide (nylon), Cellulose ester (CAB), Fluorine resin. The coating formation of these paints is due to the thermal fusion of the powder particles.

For the thermoplastic coating resins, there are Vinyl chloride, Polyolefin (polyethylene), Polyamide (nylon), Cellulose ester (CAB), Fluorine resin. The coating formation of these paints is due to the thermal fusion of the powder particles.

Epoxy, acrylic, polyester resins are used for the thermosetting powder coatings. Of those, the epoxy resin powder coating has been produced in large quantities. These resins are low in molecular weights until baked, but when thermally fused, cross-linking reaction is initiated by the curing agent in the paint, and is polymerized. Characteristics of the powder coatings are as follow.

[1] Non-solvent nature alleviates the concerns for air pollutions. Powder form makes possible for recovery and reuse. [2] Thick coating is obtained by a single coating. [3] The application processes can be automated and the coating thickness can be managed to improve product lives.

(16) High solid paints

They are essentially the same as the conventional solvent type paints but with reduced amounts of solvents and increased solids without compromising the film performance and workability, and are collectively called high solid paints. Typically, they are of 75% or more solids during painting and 70% or more solids when painted.
The coating film main elements are the same type as the conventional paints, but the viscosity of the resin itself is lowered and use co-reactive resin or low viscosity curing agent.
Some of the paints are introduced.

(1) Acrylic or polyester high solid baked paints

Single liquid type paint with low viscosity resins used for automobiles, electrical equipment, and metal furniture.

(2) Epoxy high solid paints

Modified epoxy resin paints are paints with epoxy resins partially modified with non-reactive plasticizers such as coal tar pitch, phenolic resin and others. A representative type is the tar epoxy resin paint that is lower in organic solvent content, lower in cost, is excellent in anti-corrosion properties compared to the pure epoxy resin paints.

(3) Urethane high solid paints

This is a high solid paint with low viscosity polyol and polyisocyanate compounds and uses aliphatic isocyanate curing agents. Uses are the sames as the epoxy high solid paints such as for marine vessels and chemical plant facilities.

(4) Inorganic paints

Paints with alkyl silicate or alkali silicate are used as binders. The zinc-rich paint in combination with zinc powder is well known. It is used for chemical and corrosion resistance.

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